Then you understand that "don't take pictures of mommy/daddy naked" isn't a one-time affair. It happens, we respond to it, and that repeats a few times over the course of weeks or months until the behavior stops. It's not an everyday thing (we are better stewards of our mobile devices and kids than that), but it happens.

And there are different forms of "no," there's the gentle "no" when a child takes a snack just before dinner, and there's the firm "no" of crossing a street by themselves. The first is way less effective than the second, but if you always use the second, both will be ineffective. Something like taking a picture of a parent naked isn't an emergency, it's easily reversible and relies on understanding social norms the child hasn't encountered (e.g. we'll shower with young children sometimes, we'll take them to locker rooms, etc, so there are mixed messages). So we reserve the second for true emergencies, and those lessons are learned quickly.

My point is that children are unpredictable, and often throw an annoying wrench into everyday things. Ideally, amy damage they do is easily reversible, such as deleting that nude picture from a phone a few minutes after being taken.